Various embodiments of coin operated parking meters are known in which the insertion of a coin will cause a time interval corresponding to the value of the coin to be indicated by setting indicator means with respect to a scale. Generally, parking meters consist of a coin transport and testing device, a parking time setting device for setting the parking time on the indicating means and of a clockwork which returns the indicator means in accordance with the time to the initial or zero position.
The coin transport and testing device guides a coin through several testing zones and gives one or several criterion as to whether the coin is usable so that a corresponding time may be set at the time indicator means. When the indicating means has been set to a corresponding parking time, a clockwork is started and, via a clutch device, the indicator means is driven within the indicating unit contrary to the setting direction to its initial position. Normally, the clockworks are mechanical driving means having a clock spring as an accumulator and a governor for governing the time-correct return of the indicator means. Such a parking meter is used in describing the subject of the present invention. However, other driving systems for governing the time-correct resetting of the indicator means may be used such as, for instance, synchronous motors, step switch motors and the like, which may also be used in applying the subject of the present invention.
All such parking meters are disadvantageous insofar as their indicator means may not be returned to a zero position before the predetermined time interval has expired. From experience with parking meters, it is known that the time set up by inserting one coin is very often only partially used by the car owner, sometimes it is only used up for a very short time. The remaining parking time on this parking space which has been made available to the user can be used up by the following user without the latter having paid with a coin for this time. Apart from the fact that the remaining parking time has already been paid for by the foregoing user, the following user exceeds the prescribed time limit for this parking space as, in addition to the maximum parking time available to him, he may also use up the parking time of his predecessor.
Apart from controlling the use of the available parking space, parking meters have also the object of making corresponding resources available to the communities which have to maintain the parking spaces at their own cost. It is therefore quite apparent that the revenues will be greatly increased when, each time a parking space becomes available by a vehicle leaving it, the parking meter is immediately returned to the zero indicating position. This means that the use of the remaining parking time and of time exceeding the maximum parking time is avoided. Each driver is obliged to pay the usual parking fee for occupying a corresponding parking space.
To achieve a resetting of the remaining parking times, parking meters have become known which cooperate with mechanical (U.S. Pat. No. 3,034,287) or pneumatic (U.S. Pat. Nos. 3,015,208, 3,054,251 & 3,064,416) devices when a vehicle wheel cooperates therewith.
In U.S. Pat. No. 3,034,287, a device is shown in which a movable threshold is arranged in the track of a vehicle wheel, which, due to the load, is lowered against the pressure of a spring. The threshold is in mechanical connection with the adjusting means for the time indicator via a rope or chain driving means so that, under load, the traction of the rope is loosened and a spring released by the insertion of a coin can move the indicator means to a predetermined time setting. On the other hand, when the vehicle wheel is removed from the threshold, the spring moves the threshold to the initial position, thereby retensioning the rope which moves the indicator means via a toothed wheel to the zero indicating position. To allow for this, the driving engagement between the clockwork and the time indicator is disengaged. A device of this kind means that at the place of installation, considerable measures have to be taken. Further, a permanent service has to be maintained with respect to adjusting the mechanical connecting elements.
With the devices in accordance with U.S. Pat. Nos. 3,015,208, 3,054,251 and 3,064,416, compressed air chambers are arranged in the parking space which are influenced from a vehicle wheel. Such chambers are connected via a pressure pipe with a pressure cylinder containing a movable piston within the parking meter. When a vehicle wheel on leaving the parking space moves over the elastic compressed air chamber, the air moves the piston in the cylinder and thereby via a leverage, moves an arrangement of pawls out of engagement (U.S. Pat. No. 3,015,208) so that the indicator device is unclutched and is resettable under spring action to the zero indicating position. In like manner, by means of a compressed air pulse from the elastic compressed air chamber as delivered by the vehicle wheel in the parking space, the devices in accordance with U.S. Pat. Nos. 3,054,251 and 2,064,416 release pawl and ratchet arrangements or similar clutch devices in order to unclutch the indicator means from the normal clockwork driving means. Accordingly, by means of the main driving spring of the clockwork, the indicators are quickly returned to the basic position. Also, for the last mentioned devices, constructive arrangements have to be taken at the building site which appear to be highly uneconomical especially in cases of subsequent equipment with such devices.
Apart from the mechanically or pneumatically operating devices for deleting the remaining parking times, electromechanical arrangements have also become known for parking meters. Detector means in the parking space recognize the pressence or absence of a vehicle and produce a signal which is suited to return the indicating means to zero position. As a detector means for supervising the parking space, proximity switches on the basis of changes in a magnetic field (U.S. Pat. No. 3,018,615), infrared generators, photoelectric cells, supersonic wave generators (U.S. Pat. No. 3,535,870) and others may be used as sensor elements supervising the parking space.
For instance, from U.S. Pat. No. 3,535,870, a device has become known for clearing the remaining parking time. For use as a sensor means within the parking space, a supersonic wave generator and a receiver are provided which generate pulses of a certain frequency. As long as the receiver regularly receives signals, that is, as long as the vehicle is in the parking space, this indicates that, for the internal control of the parking meter, the parking space is occupied. As soon as there are no signals returned, this signifies that the parking space has been cleared. When no return signals are received, an electronic circuit arrangement delivers a voltage to a corresponding magnet which pivots parts of the gearing means out of engagement with each other so that the clockwork driving means is disengaged between the main driving spring and the speed governor. The force of the spring then drives the time indicator back to the zero indicating position where a switch is opened so that the magnet is cut off. This arrangement is very expensive, especially with a view to the electronic circuitry,and may not be easily integrated into already existing equipment. Returning the indicator means is an additional load on the spring driving means.
In another known device in accordance with U.S. Pat. No. 2,652,551, the movable indicator means which indicates the parking time paid for on a scale is unrotatably connected to a shaft and is connected via a toothed wheel gearing and a friction clutch with a clockwork mechanism. Via a crank arm, an electromagnet is also connected to the time indicator shaft and when the electromagnetic coil is under current, the time indicator means is returned to the zero indicating position. The resetting movement of the indicator is possible when the force of the magnet is sufficient to overcome the frictional moment of the clutch since, between the indicator and the actual clockwork, there is the above-mentioned friction clutch. Between the sensor means in the parking space and the control circuit for the electromagnet, there is a great deal of electronic circuitry for amplifying and shaping the signals which are finally sent to a relay in the energizing circuit for the electromagnet. It is rather disadvantageous that such electromagnets use relatively high currents to produce a rather small movement in order to produce the necessary force. This means that there is no safeguard that the resetting to the zero indicating position by means of magnetic forces is safely accomplished.